Treatment of copper iron sulfides to form x-bornite

ABSTRACT

A METHOD IS DESCRIBED FOR TREATING CHALOCPYRITE AND OTHER COPPER IRON SULFIDES BY REACTION WITH SULFUR VAPOR TO FORM COMPOSITIONS WHICH ARE MORE RESPONSIVE TO LEACHING. THE METHOD IS AMENABLE TO CONTINUOUS OPERATION AND UNDER CERTAIN REACTION CONDITIONS IT MAY BE USED TO PRODUCE AS A PRINCIPAL PRODUCT A GRANULAR, ESY-TO-HANDLE MATERIAL INDENTIFIED AS X-BORNITE. UNDER OTHER REACTION CONDITIONS IDAITE IS PRODUCED. THE OPTIMUM REACTION CONDITIONS FOR PRODUCTION OF X-BORONITE ARE- (1) SULFUR VAPOR PARTIAL PRESSURE FROM ABOUT 200 MM. OF HG TO ABOUT 760 MM. OF HG, (2) REACTION TEMPERATUTE FROM ABOUT 460*C. TO ABOUT 500*C, AND (3) RESIDENCE TIME OF AT LEAST ABOUT 6 MINUTES. THE COPPER IN THE X-BORNITE AND IDAITE CAN BE EASILY SOLUBILIZED WITH EITHER CHLORIDE SOLUTIONS OR SULFURIC ACID SOLUTIONS UNDER OXIDIZING CONDITIONS. FOR SULFATE SYSTEMS COPPER RECOVERIES IN EXCESS OF 99% CAN BE OBTAINED BY GRINDING THE RESIDUE FROM THE FIRST LEACHING STEP TO A PARTICLE SIZE OF AT LEAST ABOUT MINUS 200 MESH AND THEN RELEACHING.

Jude i8, 1974 J. B. sRDlsco TREATMENT OF COPPER IKON SULFIDES TO FGRM X-BORNITE Filed sept. 18, 1972 4 Sheets-Sheet l .Q Mk Nl TREATMENT oF coPPER IRON sULFInEs To FORM x-BoRNITE Filed sept. 18, 1972 June 18, 197@ J. a. sARnlsco 4 Sheets-Sheet 2 m Hgh@ MW/LZ kb/w m anfmm afmmm FR MKV mwa aC OAH MWI a mw- A m W5 W01 M5 w 5 9J fw m M 5 June 18, 1974 TREATMENT 0F COPPER IRON SULFIDES TO FORM XBORNITE Filed Sept. 18, 1972 J. B. SARDISCO 4 Sheets-Sheet I5v June 18, 1974 Filed Sept. 18, 1972 J. B. SARDISCO TREATMENT 0F COPPER IRON SULFIDES TO FORM X-BORNITE 4 Sheets-Shaml 4 United States Patent O U.S. Cl. 75-1 26 Claims ABSTRACT or THE DISCLOSURE `A method is described for treating chalcopyrite and other copper iron suldes by reaction with sulfur vapor to form compositions which are more responsive to leaching. The method is amenable to continuous operation and under certain reaction conditions it may be used to produce as a principal product a granular, easy-to-handle material identified as X-bornite. Under other reaction conditions idaite is produced. The optimum reaction conditions for production of X-bornite are: (1) sulfur vapor partial pressure from about 200 mm. of Hg to about 760 mm. of Hg; (2) reaction temperature from about 460 C. to about 500 C.; and (3) residence time of at least about 6 minutes. The copper in the X-bornite and idaite can be easily solubilized with either chloride solutions or sulfuric acid solutions under oxidizing conditions. For sulfate systems copper recoveries in excess of 99% can be obtained by grinding the residue from the first leaching step to a particle size of at least about minus 200 mesh and then releaching.

BACKGROUND OF T=HE INVENTION (l) Field of the Invention (2) Prior Art In recent years the public and governmental agencies have become increasingly concerned with the degradation of the environment. In the western part of the United States copper smelters which process copper ore concentrates are regarded as one of the major sources of air pollution. Thesek smelters emit gaseous streams containing particulate matter and sulfur oxides.

Sulfur oxides, which have been found very diicult to control, result from the smelting of sulfur-bearing ores. Although copper exists in various other forms in nature, such as native copper and copper oxides, carbonates and silicates, the primary sources of copper exist as low-grade deposits of copper iron sulde ores, with the principal copper mineral being chalcopyrite.

v Instead of trying to control the emissions of air contaminants, such asV sulfur oxides, once they are formed, hydrometallurgical processes offer an alternative approach by avoiding the formation of the air contaminants. It has been recognized for Asome time that in the leaching of copper sulfide minerals, the sulfur can be recovered in solid elemental form. This is in contrast to present smelting' or pyrometallurgical processes Where the sulfur is removed by oxidizing the minerals at elevated temperatures, thereby forming sulfur oxides.

At Vthe present time in the copper industry, hydrometallurgyis generally restricted to the treatment of the 3,817,743. Patented June Y18, 1974 ice more easily leachcd copper oxide ores and native copper deposits. Aside from waste-dump leaching in copper sulde mining operations, hydrometallurgy has not been generally applied to sulfide minerals on a commercial scale. In these limited applications of hydrometallurgy, themost; commonly used lixiviants are sulfuric acid and ferrie sulfates. Of the copper sultide minerals, chalcopyrite, which is the principal copper mineral in the United States, has been found to be the most resistant to treatment by hydrometallurgical processes. Processes developed for the treatment of chalcopyrite have been plagued with low recoveries of copper from the ore. Some processes havebeen able to recover a substantial amount of the copper. in the ore but only after the leaching operation has been carried on for a number of hours which is economically undesirable. A further problem in the processing of copper iron sulde ores is the simultaneous dissolution of the iron which acts as a contaminant in the copper recovery steps. One attempt to make the copper iron suliides more responsive to hydrometallurgical processes is disclosed inl Vizsolyi et al., Pat. No. 3,459,535 (1969). Although the process disclosed in the Vizsolyi. patent results in improved copper recovery in shorter periods of time, it docs not seem amenable to commercial utilization in view of the batch operation, relatively long reaction time, material handling difficulties and failure to achieve high copper recoveries in shorter periods of time.

SUMMARY 'OF TI-IE INVENTION The object of the present invention is to provide a means for utilizing hydrometallurgical processes for the recovery of metallic copper from copper iron sulfide orc concentrates whereby conventional pyrometallurgical processes can be replaced, thus eliminating the air pollution associated with the processing of such ore concentrates. A more particular object of the invention is thel development of a process for treating copper iron sulde ore concentrates which will make the copper iron sulides,` especially chalcopyrite, more responsive to leaching in hydrometallurgical processes. Other objects and advantages of the present invention will appear from the following description, examples and claims.

It has been discovered that these objects can be accomplished and that the diiculties of prior art processes can be obviated by treating copper iron sulrde ore concentrates with sulfur vapor, thereby forming other copper iron sulfides which can be more easily leached by conventional leaching agents, such as sulfuric acid-oxygen solutions, sulfuric acid-ferrie sulfate solutions, and erric chloride and/ or cupric chloride solutions. This sulfidizing process, which takes as little as 6 minutes to complete, is preferably operated at a temperature in the range from about 460 C. to about 500 C. and at a sulfur vapor partial pressure from about 200 mm. of Hg to about 760 mm. of Hg.

In treating chalcopyrite as described, the primary product has been identified by X-ray diffraction as X-bornite. Under certain reaction conditions` idaite (usually designated as Cu5FeS6) has been formed. One of the discoveries of this invention has been the development of a commercial process for the production of these two relatively rare minerals.

The main advantage in reacting the ore concentrate with sulfur vapor instead of liquid sulfur is the physical form of the product. When utilizing sulfur vapor the product is in a granular or powder form, while lumps or other large pieces of product are formed when liquid sulfur is used as the starting material. The formation of a granular product which can be readily leachcd without further trate is reacted with liquid sulfur limits the practicality of'the process. These large pieces tend to stick to the with sulfur vapor to form other copper iron sulfide minerals. These new products which have an increased sulfur content are substantially more responsive to leaching than chalcopyrite and other non-sulfur treated copper iron sulde minerals.

sides of the container and are diiiicult to remove. Further- The reactor shown in FIGS. 1 and 2 `can be used to more,` they must be ground to a fine particle size before treat copper iron suliides in accordance with the present they can be 'effectively leached within a relatively short invention. FIG. 1 is a vertical section view of a modified period of time. Herreshoff type furnace reactor 1. Heating elements' 2' y"It has been found that by treating chalcopyrite with are used to heat the reactor and are located adjacent to sulfur vapor as much as 98.5% of the copper in the chalthe outer insulating fire brick wall 3. The ore concentrate copyrite can be recovered by leaching with sulfuric aCidis fed into the reactor via inlet star feeder 4 and conduit' oxygen solutions in as little as two hours. Ifa ferric chlo- 5. Inside the stainless steel reaction chamber 6 are five ride and cupric'chloride solution is used as the lixiviant, stainless steel plates 7 (only the bottom plate is marked leaching tests have shown that as much as 98.8% of the with the numeral 7 in FIG. 1), each having a slot-type copp'ergoes into solution in as little as 15 minutes. Moreopening for continuous ow of the ore concentrate. On over, during the leaching of the reaction product from the the center shaft 8 for each plate are mounted ve stain-f suldiz'ing process very little of the iron present as pyrite less steel scraper blades 9, as `shown in FIG. 2. The .ore is attacked by the leaching solution, regardless whether Concentrate is scraped horizontally across each plate-7 al sulfate, 0r a chloride Solution is used, 20 and drops vertically by gravity t0 the plate belOW, finally y'In seeking to maximize the copper recovery, it has been exiting the reaction chamber 6 as the reacted product found that pyrite crystals frequently prevent the copper through conduit 10 and exit star feeder 11. I iron sulfide from being fully exposed to the leaching solu- Elemental sulfur which has been liquefied outside the tion, thus preventing solubilization of the copper in the reactor is fed through conduit 12 to sulfur flash pot 13 sulfide material. To `increase copper recoveries to greater Where it iS VapOriZed. The vaporized sulfur is introduced than 99%, it has been discovered that grinding the residue into reaction chamber 6 through conduit 14. Excess sulf'rom'the initial leaching of the X-bornite or idaite to a fur Vapor exits the reactor via conduits 10 and 15. particle size of at least about minus 200 tnesh Cracks Nitrogen is introduced through conduit 16 and isused away the pyrite .grystalsa thereby exposing the remaining as a carrier for the sulfur vapor and in controlling the copper iron Snitides t0 the leaching solution; 30 partial pressure of sulfur vapor. Additional nitrogenv is BRIEF DESCRIPTION OF THE DRAWINGS introduced into conduits 5 and 10 at 17 and 18, "respectively, to malntain a nitrogen atmosphere 1n the reaction In the accompanying drawings, FIG. 1 is a section view chamber 6 and to aid in controlling the sulfur partial of a reactor that can be used in accordance with the prespressure. ent invention for the suldizing of copper iron sulfide ore The principal copper containing product (at least about concentrates. 70% by weight) has been concluded to be X-bornite based FIG. 2.is.,a top view of the reaction chamber plates upon the description of X-bornite found in an article by in the reactor of FIG. 1. Yund and Kullerud entitled Thermal Stability of Assem- FIG. 3 is a graph showing the relationship between the blages in the Cu-FeS System, Journal of'Petrology, Vol. reaction temperature and the chalcopyrite conversion for 40 7, Part 3, pp. 454-88 (1966). Pyrite as well as somev v arious partial pressures of sulfur in the suliidizing of bornite `Cu5FeS4 and idaite `CuFeS are also formed. The chalcopyrite ore concentrates. two principal products, pyrite and X-bornite, 'generally j FI'G. 4 is a graph showing the optimum residence times comprise at least about 85% by weight of the reaction inthe suldizing `of chalcopyrite ore concentrates. product. Table I below presents X-ray diffraction pattern `FIG. 5 is a graph showing the percent copper extracted 45 data for material produced by suliidizing chalcopyrite ore by sulfuric acid leaching for X-bornite and idaite as cornconcentrate in accordance with this invention as compared pared to non-suldized copper-containing materials. to the data presented for X-bornite in the Yund'et al. FIG. 6' is a ow sheet of the process of this invention article and standard data for bornite, pyrite and other for the production of metallic copper from chalcopyrite minerals.

. TABLE 1 Pattern data of sample Standard data for- X-bornite Pyrite Idaite Bornite SiO: (quartz) Most Chalcopyrite 2a I D D 1/1 max, D r/rmax, D 1/1 max. D r/I max. D 1/1 max.' D 1/1 max. D` I/r max lg i2 i111 "j 35 6'15 100 271 6g gg :36: 3343 27. 9s` 40 3. 28.66 160 3.12 29.40 46 3.04 r31. 84 20 2. 808 32.80 25 2.728 33.10 260 2. 704 2 37.12 160 2.420 40.80 110 2.210 47.00 30 1.932 47. 50 21o 1 91 48.20 30 1.886 y66. 32 160 1.632 1.630

NOTE: 20=angle of detection. I=intensity in counts per seeond.D =interplanar spacing in Angstrom units. I/I max.

ore concentrates utilizing sulfuric acid as the leaching In accordance with the present invention chalcopyrite =relative intensity in percent;

The material for which X-ray diifractionrdata are presented in Table I was produced by treatingfchalcopyrite ore concentrate with sulfur vapor maintained at a partial pressure of 200 mm. of Hg for 13 minutes. .The reaction temperature was 471 C. and sulfur/copper molar v'ratio andother copper iron sulfide ore concentrates are reacted. of the feed material to the reactor was 1.3. The Chalco;

For,example,`the peak at a 2Q value of 47.50 has `a much higher intensity relative'to the peak at the 20value of 56.32 ,than it has ina known pyrite' sample."The peakV at the 20 value of 47.50"r in the Table I sample is about 140% of the 1peakatthe 20 value of 56.32, while in a` about 40% oftheY peakknown V-pyrite sample it is only at'the 20 valu'eof 56.32", v'

Consequently, to obtain -a more positive identification of the X-bornite, a known sample Vof 'bornite was reacted with sulfur vapor under similar reaction conditionsVThe onlydiferent reaction conditionrwasjthe jusje of a 1.04 sulfur/copper ymolar feed ratio. The X-ray diifraction data for .the product' material is presented in Table 1I and Vin? dicates, `based on the data from Vthe Yund et al article,

6 Yund'article or other prior art of the means for producing X-bornite on a commercial basis as is disclosed herein.

'The reaction temperature for producing X-bornite can range from the temperaturat which sulfur vaporizesg about 440 C., to about 530 C. The optimum temperature .for suldizing chalcopyrite ore concentrates has been found to be in the range from about 460 C. to about 500 C.

In treating chalcopyrite ore concentrates, partial presi sures of sulfur above approximately 200 mm. of Hg promote the'preaction with chalcopyrite. Increasing thesulfur partial pressure from about 200 mm. of Hg to about one atmosphere does not seem to affect the reaction one way or the other. Sufficient sulfur should be initiallyv fed to the reaction vessel to maintain the partial pressure at approximately 200 to 760 mm. of Hg. It has been found that this can usually be accomplished by using a sulfur/ coppermolar feed ratio from about 1.2 to about 1.6. To keep the desired sulfur partial pressure additional sulfur is suppliedduring the reaction to provide for replacement of the reacted sulfur. IFIG. 3 shows the percent conversion of lchalcopyrite as a function of temperatureand .sulfur partial pressure.

A minimum residence time (deiined as the time the ..0re remains in the reactor) of about 6 minutes is necessary for obtaining a high conversion of chalcopyrite dur ing the sulfidizing reaction at optimum conditions. This is shown by FIG. 4. This graph in FIG. 4 also indicates that an increase in the residence time has no significant effect in reducing the amount of residual chalcopyrite in the reaction product.

, a If the reaction product consisting primarily of X-bornite is kept at the reaction temperature under a nitrogen atmos-1 phere for an additional period of time, a different prod` uct is formed which is primarily bornite. This can be seen from Table III which shows X--ray diffraction data for the nal reaction product resulting from heating sulfidized chalcopyrite at 471 C. for 12 minutes in a nitrogen The true relationship of X-bormte to bornite 1s not atmosphere.

' TABLE III Standard data for- Pattern data. of` sample -Bornite Pyrite X-bornite Idaite S102 (quartz) MoSz Chalcopyrrte ,i

26 .I D D I/I max. D I/I maxi. D I/I max. D I/I max. D I/I max. D I/I max D I/I max.A

14.50 10 6.10 6.15 100 -'--..'...i. 20.98 `15 4.23 Y v 55.34 200 1. 632 39.06 i V25 i. 61.70 35 l] 64. 32 .35

." NTE: 20=angle oi detection. I=intensity in counts per second. D=interp1anar spacing in Angstrom units. I/I maxsrelative intensity vin percent..

exactly clear, as is indicated in the Yund article. Yund and Kullerud suggest that X-bornite contains slightly more sulfur than stoichiometric bornite. CFeSl. The reaction of sulfur with chalcopyrite to produce X-bornite is probably similar to the reaction producing bornite which is as follows: A

During theoretical phase relation studies, Yund and Kullerud were able to produce X-bornite by annealing` sulfur-rich synthetic bornites ata temperature below ap-r. proximately C. Although X-bornte occurs in some geological envirernnents,V there is, nofzsuggepstion (in the 7.5 at 471 C. for 13 minutes. The sulfur/coppermolarlfeed' 'Under ptimilm lreaction conditions the amounn--of `residual chalcopyrite in the reaction product is approxi matelyf1-3% by wet chemical` analysis. To further ref duce the residual chalcopyrite, the reaction product can.

' idaite is similar to X-bornite in its responsiveness to leaching. Table IV presents X-ray diffraction` data for theV re-` action product of recycling-the initial reaction product ratio was 1.39 and the sulfur partial pressure was maintained at 208 mm. of Hg.

Solid sulfur and chalcopyrite ore concentrate were inserted into the reactor and then heated to 475 C. The resulting TABLE IV Standard data for- Pattern data ol sample Idaite Pyrite X-bornite S102 (quartz) Chalcopyrite M052 29 I D D I/l'. max. D I/I max. D I/I max. D I/I max. D I/I max. D I/I max.

14.52 35 6. 10 6. 15 1001 20. 15 4 44 20.96 4.23 35 23. 90 20 3. 72 26. 68 35 3. 34 100 27. 32 55 3. 26 27. 62 40 3. 23 M .Se 28. 54 29. 46 20 3.03 3 03 100 31. 74 160 2. 817 32.04 130 2. 791 33. 14 220 2. 701 36. 60 20 2. 453 2. 456 37. 16 125 2. 417 40. 86 125 2. 207 42. 52 20 2. 124 47. 52 130 1. 912 48. 20 155 1. 886 49. 36 115 1. 845 1. 845 56. 34 205 1. 632 1. 633 100 1. 630 21 56. 92 35 1. 616 1. 618 10 59, 04 80 1. 563 1. 564 30 1. 564 14 l. 559 7 61. 74 45 1. 501 1. 502 20 64.36 55 1.446 1.448 24 N o'rE: 28=ang1e of detection. I=intensity in counts per second. D=interplanar spacing in Angstrom units. I/I max. =relative intensity in percent.

The sulfidizing of chalcopyrite and other copper iron sulfide minerals is especially adaptable to continuous processing techniques. The reaction time is relatively short and the reaction product can be easily handled and transported since it is in granular form.

In contrast to the vapor-phase reaction of the present invention, the liquid-phase reaction of the prior art, that is, heating a mixture of solid sulfur and copper iron sulde ore concentrates to the point where the sulfur is liquefied and even possibly vaporized, results in a reaction product which presents difficult material handling problems. Large pieces of product, which has been found to be mainly idaite, are formed, and frequently the product sticks to and fouls the walls of the reaction vessels. Consequently, before leaching the liquid-phase reaction product must be ground to a line particle size. In addition, due to the fouling of the reaction vessel the liquid-phase reaction presents difficulties for normal batch and continuous processing.

In the vapor-phase suldizing of chalcopyrite, th particle size of the products is actu-ally less than that of the incoming chalcopyrite ore concentrate. 'For example, the mass mean diameter of the chalcopyrite ore concentrate particles was 0.091 mm. with only 48 weight percent passing through a 200 mesh screen. After vapor-phase suldizing the chalcopyrite ore concentrate, the mass mean diameter of the resulting product particles was 0.068 mm. with 87 weight percent passing through a 200 mesh screen.

The objective of the suldizing reaction is to produce a copper iron sulfide material from which the copper can be quickly leached in appreciable quantities by conventional leaching agents, such as sulfuric acid-oxygen solutions, sulfuric acid-ferrie sulfate solutions, and ferric chloride and/or cupric chloride solutions, at relatively low pressures and temperatures.

A method for pressure leaching of chalcopyrite with sulfuric acid and oxygen is reported by Vzsolyi et al. at page 52 of the November 1967 issue of the Ioumal of Metals. To obtain at least 98 percent solubilization of the chalcopyrite within three hours, the particles had to be ground to a size where 99.5% passed through 325 mesh screen and 50% stoichiometric excess of sulfuric acid was required. The oxygen partial pressure and temperature were maintained at 500 p.s.. and 116 C., respectively.

In U.S. pat. No. 3,459,535, Vzsolyi et al. described a process for leaching a covellite-pyrite material with oxygen and sulfuric acid at 90 C. and 70 p.s.i. of oxygen. The covellite-pyrite material was prepared by reacting sulfur with chalcopyrite in a batch reactor at 475 C. for 2 hours.

material had to be broken up and ground before leaching to a particle size of substantially 100% minus 325 mesh. During the leaching step, ve hours of residence time was required to obtain copper extractions greater than 98.5 weight percent, and under these conditions 53 Weight percent of the iron from the pyrite was leached.

By my invention over 98.5% of the copper can be solubilized in as little as tWo hours by leaching the suldized copper iron suldes With sulfuric acid and oxygen. For one set of examples, the copper iron sullides from the vapor phase reactor were not ground as in prior art processes but were only screened to remove the plus 100 mesh size particles and then pressure leached in an autoclave using only one stage. Table V below shows: (A) the composition of the copper iron suldes resulting from the vapor phase sulfidizing of chalcopyrite ore concentrates; (B) results of leaching tests on suldized ore; (C) results of leaching tests on chalcopyrite ore; and (D) reaction conditions for these leaching tests.

TABLE V.-CONDITIONS AND RESULTS FOR PRESSURE LEACHING USING SULFURIC ACID AND OXYGEN A.Compositions of the copper iron suldes (suldized ore) West chemical analyses (wt. percent) Suldized ore sample Cu Fe S X-ray diiraction analysis No.1 24.71 24.19 36.19 23% chalcopyrite; remainder -bornite and pyrite. No.2 24.71 24.90 36.10 45% chalc0pyrite;3%idaite; remainder is X-bornite and pyrite B.-Leaching tests on suldized ore Resi- Wt. percent Material balance Sulildxzed dence solubilized (wt. percent) ore samtime ple No. (hrs.) Cu Fe S Cu Fe S C.-Leaching tests on chalcopyrite ore nitrogen atmosphere prior to leaching.

D.Reaction conditions Temperature: 70 C.

Oxygen partial pressure: p.s.i.

Stirrer speed: 1,500 r.p.m. Wt. percent of sulfuric acid in leach liquor: 13.0%.

Grams of leach liquor per gram of sultldized ore: 3.76.

' -It can be seen from Table V that only 5557% copper is solubilized when leaching chalcopyriteore as compared to 98.5'99.0% solubilization when leaching sulidized ore. Moreover, only 27-37% of the iron in the sulidized ore Awas solubilized.l Y

The data in Table VI show the advantage of leaching X-bornite or idaite over native bornite or covellite ore. All the leaching tests were made at an oxygen partial pressure of 70 p.s.i. andA 105 C. using Vabout V13.70 wt. per- 'cent sulfuric acid and 3.7 grams of acidic solution per gram of ore material. vStirrer speedV was 1500 r.p.m. and particley size of the ore material was minus 200 plus 325 mesh. Table VI and FIG. Vshow the results of these leaching `tests and illustrate the signicant difference in the leaching characteristics of the different materials. The suldized materials, idaite and X-bornite, are considerably more susceptible to acid leaching than the other materials.

10 stantially all or in excess of about 99% of the copper in the copper iron sulides produced by the use of the vapor phase suliidizing reaction. It has been found that extensive grinding of the suldized ore prior to any leach ing does not materially enhance the solubilization of the copper.

To illustrate this method for Amaximizing copper recovery, copper iron sulfide-pyrite products from the vapor phase suldizing reaction were screened to obtain a particle size of 100 percent through 100 mesh. This material was pressure leached in an autoclave with sulfuric acid and oxygen. The washed residue was ground to minus 325 meshor Vminus 200 mesh to cracldaway the pyrite crystals and releachedwith fresh leaching solution. The conditions and results for both stages of these tests are given in Table VII.

TABLE Vlr-CONDITIONS AND RESULTS 'VFO RE LACHING USING SULFURIC ACID AND Y Chemical analysis l of spent residue Resl- Initial Material balance i Wt. percent dence wt. (wt. percent) solubilized Acid Copper Copper time percent soluble as chalas chal- Test number Materiel leached (hrs.) H9804 Cu Fe Su Cu i Fe S copper cocite copyrite 1 X-bornitel 1 Y 12.98 101.7 96.6 93.3v 97.0 30.6 11.6 .51 .43 .3 2. dol- 1.5 i 12.98 102.8 Y' 101.1 95.1 95.1 27.5 10.2 .45 .39 .25 3.... ...110 l 2 12. 98 102. 3 99. 4 97. 7 98. 5 37. 4 11. 7 14 15 4.- Native covellite--- 1 12. 98 94.1 87. 7 96. 4 58. 0 19. 6 8. 4 5-. 1.5l 13.13 93.1 83.8 94.2 67.0 24.9 4.7 6-. l2 l13. 13 92.5 85.2 91.3 79. 2 26. 8 -5. 1 7.. 1 13.13 100. 1 118. 9 97. 4 79. 2 58. 7 '-44.1 8.. 1.5 13.13 102.3 103.0 90.6 87.0 72.0 .-39.5 9-- 2 13.13 99.8 100.4 94.2 92.6 l 78.1 33.7 10- 1. 5 12. 97 101. 3 103. 4 102. 2 93. 8 20. 9 3. 2 11 2 12 97 97.0 103.4 105.1 94.3 21.0 3.7 12. 2 13. 13 101. 0 104. 0 98. 7 95. 9 24. 1 5. 13. 1.5 13.13 105.3 104. 2 87. 1 89. 8 18. 2 13. 14- 2.5 13.13 102.2 98.6 95.0 97.0 33:5 11.1

l Composition by X-ray difractionis mainly X-bornite and pyrite with about 4% chalcopyrite and some idaite. j 2 Composition by X-ray diiraction is mainly idaite and pyrite with about 1% chalcopyn'te and some X-bornite and bornite (vaporphase preparation).

TABLE VIL-CONDITIONS ND RESULTS FOR THE TWO-STAGE LEACHING TESTS Wt. percent Wt. percent Material balance Resi- Gms. solubilized across solubilized across across one f. Y l y Total dence H1801k onerstage both stages stage (wt. percent) l Material Size of press time per l Test No.l Stage leached material p.s.i. ,hr. gms. Cu Cu Fe Fe S 1 X-bornite -100 88 2 2.0, 96.6l 48.2 23.6 92.7 93.2 2 Residue Stage 1.-. '-325 88 1 5 92.0 39. 9 24. 5 86.9 89. 9 1 x-bornite 1oo se V'a 2.o 82.7 y 4&7 24.8 92.9 91.2 2 Residue state -325 l 2 Y 11.8 94.7 47.1 29.0 98.5 81.2 i X-bornite -109' ss 3 1 2.o 96.1 55.3 29.4 90.9 90.9 2 Residue stage 1-.. -325 88 1 29.7 87.2 Y 34.5 Y 17.5 97.7 Y 88.1

1` X-bomne 1oo es 2 2.9 99.7 4.15 24.6 82.9 sae 2 Residue stage 1. -325 68 2 32.3 91.5 44.8 30.8 98.0 83.8 1 X-bornite 190 `68 1 2.0 87.2 28.8;V 5.9 87.9V 92.9 2 Residue Stage 1. -200 68 1 15.19 67. 6 23. 4L 16. 3 103. 9 489. 8 1 X-beniire -1oo vSe'- 1 2.o @99.5 95.4 9.9 97.7 92.1 2 Residue stage 1...' A``200 88 19.3"k 75.7` 27.9 15.4 101.0 91.0 1 Kommte.-- -190 ss 2` 2.oy 95.8 49.9 22.1 ses 91.0 2 Residue stage '-200 y88 1 49.2 78.2 29.2 15.3 102.6 95.9

8 -n 1 X-bornite -325 88 2 2.0' 95.7' 37.7` 15.0 108.5 93.9 2 Residue stage 1.... -325 68 2 47.7 94.0 55.7 26.7 89.4 88.0

is to providea method for leaching the copper entrapped by the pyrite crystals.

i I have unexpectedly discovered that by grinding the residue from a one-stage pressure leach reaction, during which most (at least about 80%) of the copper was solubilized, the pyrite crystals c an be cracked away, therey by exposing the remaining copper iron suldes to the leaching agents. By this method I can solubilize sub- 'Ihe` resulting pregnant liquor from the pressure leach reaction vcontains an appreciable amount of iron which must be removed before the copper sulfate solution ca n be treated by electrolysis to produce metallic copper. Excess iron in the electrolytic cell reduces the cathode eiciency and ,can contribute to contamination of the copper.I

AIt has been found that the iron can be removed by precipitating it as a jarositic iron oxide-sulfate.l The ratio of sulfate ions to iron in the combined precipitate has been found to be essentially that of the ,compound jarosite. It is precipitated from an acid solution at pH values of 1.5 and above. Since the pregnantliquor from the leach reaction contains excess sulfuric acid, the pH values range from 0.5 to 1.0. Thus, before jarosite can be precipitated the excess sulfuric acid must be neutralized. In the present invention the neutralization 0f the sulfuric acid can be ac- .1 1 .complished with cement or scrap copper according to the following equation:

(2). j cu+H2so,- cus`o4'+H- The oxidation state of iron in jar'osite is +3, thus any 1-2 The conditions and results oftypicalelectrowinning vtests are showninTable IX: J

TABLE 1x.REsULTs AND CONDITIONSv FOR ELECTRO- ,WINNING TESTS 'Y r'rst bVV -..'1 2 ferrousions 1n the liquor must befoxidizedto ferricions. e num r Y Conditions:l Y v This 1s accomplished by oxidation with oxygen as follows. @C Itlpertu S., C 23g 23g 23g 1' oagevos Sodium ions for the jarosite formation can be supplied I 'lqed 3 5 3 5 3 4 by such sodium compounds as sodiumhydroxide or s o- 041g gg 2.?

dium carbonate. When sodium hydroxide` is used, i t is Contgc'gngsjjj j 21 21' 9 believed that the reaction proceeds as below: B85111151 t 1 1C) urren i; efficiency (percent)... Green C0 er IGmOVe v (4) 3Fe2(S )4?3+2NaOH+1OHOH- Rate of coer depletion (gm Ihr ..0. 97 2.3

a. The reactionsabove can be 'carried'. out in 'one"reactor, or the cement copper and the sodium hydroxide can be added prior to the oxidation step. The reaction has been carried out in a standard autoclave in which the pressure leach tests were conducted.VV The pregnant liquor, cement 20' High temperature was used because it produced a more easily lterable'precipitate. The oxidation rate-off-the ferrous ions to ferrie ions increased with the use of high pressure. f v v A number of'runs were made during which about 80 percent of the iron in the pregnant liquor was removed. Very little copper remained in the residue with the iron. For these tests, enough cement copper was added to the liquor to bring the pH up to 1.5-2.0, and enough sodium hydroxide was added to satisfy the reaction of equation (4). The conditions for carrying out these tests were as follows: f

Table VIII below contains the conditions .and'results' of these tests.

YAnother advantage ofthe above-described method'is that the purification of cement or vscrap .copper can be incorporated into the overall'process. As was discussed previously, cement-or scrap copper is added to thesystem to neutralizeexcess.sulfuric acid in theiron removal step.

One embodiment of the process according to the present invention wherein sulfuric acid is used as the leaching agent is shown by the How diagram in FIG. 6.

In treating chalcopyrite ore concentrates,the ore concentratesjare added to suldizingreactor 101VV through line 102., Molten rsulfur is introduced into' reactor 101 through line 103 wherein itis vaporized before being mixed with the ore concentrates. The vaporized sulfur is preferably maintained at a partial pressure of at least about 200 mm. of Hg. In the reactor the ore concentrates are sulfidized in as little as six minutes at a temperature of about 470 C., thereby converting most of thechalco'- pyrite to X-bornite and pyrite. Excess sulfur is Adischarged through line 104.

p.s.i. Y tl'lrugh line 108 .u The acid oxidation leach solution at a temperature of about 105 C."so1ubiliz`es"1ost of the'coppenin the ore in about two hours.

The leach slurry from the primary leach stage is then transported through line v109 to primary separation device TABLE vnrcoNnITIoNsANE REsULTs For. IRON REMOVAL TEsTs Material balance Iest No. feed Cu Fe S :copper' NaOH .Cu Fe S pH Cu Fe S- Cu I e S 300 5.89 1.89 ,4.27 3.0: 1.1 5.89 .'16 3.2 1.1 0.9 93.3 85; 600 5.75 1.96 9.0 2.0 6.32 29 1 1 1.0 '102.7 94. 600 5.65 .1.72 4.04 10.75 v2.2 @7.29 .29 3.72 1.2 90.8 98. 600 5.65 1.12 3.51 t 10.0 l 0 4:47 2.6 101.9 77`. 1, 263 9 .03 1 .79 5 .87 30 4.8 4.39 .14 2.08 1.3 81 .8 81 300 6.94 1. .5,58 v 0.- 15 6.217 .24 4.89 3.4 98.8 81.

N OTE- Analysis of cement opper used in wt. percent:` (3u-83.6%, Efe-5.0%, yS-0.4%.A

After about 80% of the iron haslbeen removed'from 'the pregnant liquor, the Vsolution contains approximately f .6-8%. copper, 0.2-0.4% iron, and l`3%f,e sulfuric acid. Thel copper in lthis solution can b e recovered in r`metallic form by conventional electrowinning methods. 'Equation' (5)v sets forth the reaction in the electrolytic ceu: .1L 1

(5) Electrolysis n, Cuso. H10 Cu -l- Hgso. 71- 1/2o, About 60% of the copper in the copperfsulfate -solu-4 tion is removed during electrolysis at the `following con-f .ditionsz A j Temperature: SiO-50 C.

.Contact Time: 14-21 hrs.

Voltage: 1.6-2.5 volts Current Density: 7 to 25 (amps/sq. ft.) ACurrent Efficiency: About 85% 110. In this device'the solids consisting primafilyofa small amount of unreacted copper iron suldes, elemental sulfur andinsoluble residue are separated from the solutioncontainingcopper sulfate, ferrous sulfatearid unreactedv sulfuric acid. The solids are transported'through line -111 to grinding stage 112'and'the'solution'goes-'to -'ir'mreinoval stage 114- through line 113. f v f In'the grinding stage -the solids are further `ground by use of conventional size reduction equipment to at least about minus 200fmesh. The ground solids areithen trans'- stage: AThe resulting slurry is then transported to'second- 75 ary'separation device 120 through line 11'9.l

. 13 Y f .Iu deyice 120 conventional separation means are used to separate the solution containing excess sulfuricA acid, lferrous sulfate and copper sulfate 'from the solid material `consisting primarily of elemental sulfur and insoluble residue which is discharged through line 121. If desired the elemental sulfur canbe separated from the residue by means known to those skilled in the art. The solution is discharged from device 120 through line 122 and is combined with the regenerated sulfuric acid `solution that is added to the primary leach stage through line 107.

, In iron removal stage1114 the pregnant liquor containing copper sulfrate, ferrous sulfate and excess sulfuric acid is first treated to neutralize the excess sulfuric acid by the addition of cement copper throughline 123. Oxy- Igen sutlcient to maintain a partial pressure of about 70 p.s.i. is added through line 124 to oxidize the ferrous ions to ferric ions and sodium hydroxide is added through line `125 to precipitate the ferric iron as `jarositic iron oxidesulfate. The preferred reaction temperature is 115 C. and the normal contact time is about 1-2 hours.

. The slurry from iron removal stage 114 is transported through line 126 lto iron separation device 127 wherein the jarositic material is separated from the solution containing primarily copper sulfate and some ferric sulfate. The jarositicimaterial is discharged through line 128 and the solution is transported through line 12.9 to electrolytic cells 130. The jarositic material may alternatively be recycled to either the primary or -the secondary leach stage for the removal of any copper therein. In such case the jarositic precipitate would be removed from-the process with the insoluble residue.

The solution in cells '130 is electrolyzed to produce metallic copper and to regenerate sulfuric acid. Metallic copper is removed at 131 and the regenerated sulfuric acid solutionwhich is used in both the secondary and primary leach stages is discharged through line 107. f

The X-bornite and idaite prepared by the process according to the present invention offers a considerable advantage in the use of lferrie chloride and/or cupric chloride as the leaching agent. Considerably more copper can be leached from X-bornite or idaite than chalcopyrite during a given period of time. Table X contains conditions and results for atmospheric pressure leaching of X-bornite and chalcopyrite using ferrie chloride and cupric chloride, along with sodium chloride which acts to keep cuprous chloride in solution and is believed to aid the reaction.

Note from Table X thefast rate of the dissolution reaction `with ',X-bornite. Within 15 minutes more than 98.5% of the copper was solubilized. Underpthe same conditions only 51%f of the copperin the chalcopyrite was leached. v, What is claimedis: .1

" 1.V In the 'processing of copper iron sulfide oreconcentrates for the hydrometallurgical `production of metallic copper wherein the` ore concentrates are leached with a Hg and the reaction temperature is in the range from about 460 C. to about 500 C.

` 3. The method according to claim 2 wherein the ore concentrates 'consist primarily of chalcopyrite ore Vconcentrates and the chloride leaching solution contains ferric chloride and cupric chloride. v 4. In theprocessing of chalcopyrite ore concentrates for the hydrometallurgical production of metallic copper wherein chalcopyrite ore concentrates are leached with a sulfate solution, an improved 4method .of making the chalcopyrite in the ore concentrates more responsive to PHERIC PRESSURE LEACHING USING FERRIC CHLO- RIDE AND CUPRIC CHLORIDE A.Reaction conditions B.-Leaching tests on sultided ore v Material Gms. l Wt. percent balance (wt.

NaCl/ vReaction solubilized percent) gm A time Test No ore' (hrs.) Cu Fe Cu Fe l 0.8 l 0. 5 98. 7 14. 5 105. 6 102. 7 0.8 0.25 98.8 17.2 101.8 95.5 .1.0.H a 0.2@ 99.4 f 26.2 89.4 92.

C.Leach ing .tests onchalcopyrite ore a a v Material Gms. Wt. percent balance (wt. NaCl/ Reaction solubilized percent) gms. time Test N0 ore (hrs.) Cu Fe Cu Fe Noria-The residue cake was washed by re-slurrying with dilute hydrochloric acid.

said sulfate leaching solutionA which comprises reacting sulfurv vapor with the ore concentrates at a sulfur partial pressure of at least about 200 mm. of Hg and at a reaction temperature in the range from` about 440 C. to about 530 C. for such a period of time as to form a reaction product with at least about of the copper-containing materialin the reaction product being x-bornite.

5. The method according to claim 4 wherein the sulfate leaching solution contains sulfuric acid and oxygen.

6. The method according to claim 5 wherein the reaction temperature is in the range from about 460 C. to abput 500 C. a i (t 7. In the processing of copper iron suliied ore concentrates for the hydrometallurgical production of metallic copper, the method of solubilizing substantially all of the copper in the copper iron sulides which comprises:

(a) reacting sulfur vapor with the ore concentrates to i form a reaction product consisting principally of Acopper-containing material and pyrite, with at least about 70% ofthe copper-containing material being (b)` ,leaching the reaction product from step (a) to h solubilize most of the copper in the reaction product;

(c) grinding the solid residue from step (b) to a para ticle size of `at least about minus 200 mesh; and

(d) leaching the ground residue from step (c) to solubilizesubstantially all the remaining copper in the a reaction product. i

8a.z The method according to claim 7 -wherein the leaching in both steps (b) and (d) is performed with a sulfuric acid solution under oxidizing conditions. A, i v' 9. The'l method according to claim 8 wherein the ore concentratesmconsist primarily of chalcopyrite ore concentrates.

- 10. The method according to claim 9 wherein the sulfur vapor'is maintained in step (a) at a lpartial pressure of at least about -200 mm. of Hg and the reaction temperature Erg: (a)`is inthe range from about 440 C. to about V11.` The method according `to claim 7 wherein the leaching is performed with a ferrie chloride-cupric chlo- 0 ride solution.

12.A method for the hydrometallurgical production of `metallic copper from copper iron sulfied ore concentrates which comprises: i

(a) reacting sulfur vapor with the ore concentrates to form a reaction product with at least about 70% 15 o f the copper-containing material in the reaction product with at least about"70? v of the copper-:con-

taining material inthe reaction product b eing .X-.borfnit f v j (b) leaching the reaction-product from'step (a) with a sulfuric acid solution under oxidizing conditions to s olubilize most of the copper inthe reaction product; I f (c) grindir1 g the'solid" residue from; `ste`pf (b) vt'o' z i pat ticle sizeof atleastabout minusi'200`mes`h'i.'

"(d)` leaching the ground residuefromstep (c) with a sulfuric acid'fsolutionunderoxidizi' g' Conditions' to solubilize' s ubfsta'ntiallyall, the remaining copper in thereactionproductof step (a f *(e) oxidizing the solution "containing the" solubilized `copper toY precipitate iron from ythe's'lution; and

(f) electrolyzingthe solution from Iwhich ftheirl'oii has been precipitated to produce metallic'copper'Jand to regenerate sulfuric acidV solution for reuse the "'leaching'steps. 13. .The method according solution containing the s olubilizedcopper Ais 'reacted with 'ce-mentcopper to raise the pH of thesol'utio'n to atleast 1.5 andwherein oxygen and amaterialselected fromthe group consistingof sodiumcarbonate yand' sodium 'hydroxide arefadded to the solution toi precipitate the form'ofjarositic iron `o xide' sult'a te.l 14.' The meth'od according to cl im 13 wherein h eoxi'jdation step (step (e))'is perform'edat a' temperature of at least about 115 C. and at an oxygen partial pressure of about 70 p.s.i. 15. The method of claim 12 wherein the o re concentrates consist primarily of chalcopyrite oreconcentrates. 16. The method of claim wherein the sulfurvapor reacted with the ore concentrates in step (a) is maintained at a partial pressure of at least about 200 min. of Hg and the reaction temperature for step (a) is'iri range from about 460 C. to about 500 C. 17.'The method of claim 16 wherein only th'esolution 'containing the solubilized copper from step`(b is o xif dized in step (e) and the solution containing `the"solubi lized copper from step (d) ^is `recycled along with the regenerated sulfuric acid lsolution vfrom 'st ep' ."(`f) to 'step(b). -1 18. A method for the vl'r'ydrometallurgical v r oductiori on in lthe of metallic copper from copper iron sulfide Qreconcentrates'containing primarily 'chalcop'yr'ite' which comprises:

(a) Vreacting the orev concentrates Awith sulfur'k vapor at a partial pressure yof atleast about 200mm; of Hg and 'at a temperature in the range'froni about460 C. to about 500 C. for atnleastabout `6 t rn inu.t es to form a granular reaction product with at least about 70% of the copper-'containing material 'in the 'reac- Vtion product being X-bornite.` y (b) leaching the reaction product from step (a) with a' sulfuric acidy solution under oxidizing conditions to' form a slurry-containing' sulfur, solid s, excess sulfuric acid, copper sulfate, and ferrousf sulfate, therebysolubilizing most ofthe copper in the reaction product of step A(a);

(c) separatingthesulfur and vthe V'solidsin theuslurry of step (b') from the solution containingfthe ,copper sulfate, ferrous sulfate and excess sulfuric'acid; v(d) grinding-the solids and sulfurfrom. step (c). to a particle size of at least about minus 200. rnesh; y

(e) leaching the ground solids and sulfur ,from step (d) with: a sulfuric acid solutionu nder oxidizing conditions to form a slurry containing sulfur, solids,

- copper sulfate; ferrous Isulfate, and excess sulfuric acid, thereby solubiliz'ing substantially all thefremai11` ing copper in the reaction product of step1('a);

-step (e)' from the' olution containing the fcopper sulfate, ferrous sulfate and excess sulfuricjacid;

16 (g) reacting cement copper with the solution of step (c) to raise the'pH of the solution to at least about "1.5; v l n (h) `'reacting sodium hydroxide and oxygen at a partial prsssure of atleast about70 p.s.i. with the solution :of step (g) at a temperature of at least about 115 "C. to precipitate ironin tl 1e form of jarositic-iron oxide-sulfate; 5 r (i) electrolyzing-'the solution from" which the iron has vbeen "precipitated to *produce metallic copper and to regenerate sulfuric acid-solution; and. l' (j) 'recycling-the sulfuric acid solutionof step (i) to step-(e) and lalongrwiththe solution 'of step (f) .to

step (b) for use in further leaching." l 19. I 'n a hydrometallurgical process for treating copper iron-sulfide ore `concentrates for theffproductio'n of metallic"c'op"p`er"VA comprising suliidizing the' ore concentrates, leachingthe sulfidized ore concentrates to solubilizethe copperf'and recovering l'metallic copper from the leach solution, the improvement wherein said suliidizingfcom'- prises reacting s ulfurvapor with the ore concentrates to form a reaction product with'at least 'about-70% ofthe coppe'ncontaining material in the reaction product being X-bornite.' i'

` 20. vThemethod according 'to claim 19 wherein the Vore 1 concentrates consist essentiallyof chalcopyriteY ore conce'ntrates'and the reaction productcomprises principally copper-'containing material and -pyrite.

2'1. -The method according to claim 19 wherein the ore concentrates consist'essentially of bornite ore concentrates. 22.` The'method according lto claimf'19 wherein the' X- bornite is further reacted with additional sulfur vapor to form idaite.

23. The method according to claim `19 wherein the sulfur vapor is maintained at a partial pressure in the range from about 200 mm. of Hgzto about 760 mm. of Hg.

24. The method according to'clairnv 23 wherein the reaction temperature is in the rangel from about 440 C. to about'530" C. t

25. lThe method according to claim 24 wherein the reaction is maintained for at least about 6 minutes.

26. In a hydrometallurgical process for treating copper iron sulfidev ore concentrates containing primarily A'chalcopyrite'fore concentrates for theproduction of metallic copper comprising suliidizing the ore concentrates, leaching thesulidized ore concentrates to solubilize the copper and recovering metallic copper from the leach solution, the improvement wherein said suldizing comprises reacting the ore concentrates with sulfur vapor at a partial pressure of above about 200mm. of I- Ig and ata temperarture" in the range from abot'460" C;- to about 500-IC. for at least about 6minutes to form a reaction product with at least about 70% of the copper-containing .material in the reaction product beingX-bornite. Q v

l. I v jReferences Cited f UNITED ySI`iil'I`I-S PATENTS 3,637,371 1/1972 Machin et al 75-117 X 2,746,859 5/1956v McGauley et al. 75-1 X 3,351,462 .l1/19.67... Arentzen et al. 75-73 X 3,169,853 2/1965 Van Es 75-104 X 1,736,659 11/.1929 Mitchellgn; 1-- 75--104 X c 3,574,599' 4/19731V YOrtloff et al. 75-104 3,490,899 f 1/1970Y Krivsky 7572 X 3,656,937 4/1972 Gandon et al 75--117 X FOREIGN`PATENTS 1V 1 ,059,476 2/1967""G reat Britain" 75.-2 3,191 1905 Great Britain 75--74 '1ers-772,104, 11s, 117

ALLEN B. CRTIS, Primary i xamiiier U.s. o1. X11.

. UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,817,743 Dated June 18, 1974 Inventor) John B. Sardisco It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 3, Table I', first numeral under 2Q Column heading,

"14.58" should read 14.48

Col. 7, Table IV, first numeral under M082, I/I max. column heading,"l00l" Should read 100 Col. .7, line 86, "pat," should be Pat.

, Col. 8, Table V., the heading "West chemical analyses" should be Wet chemical analyses Col. 9, Table VI., first numeral under Copper as chalcopyrite column heading, 3" should be .30

Col. 9, Table VI., under Material balance (wt. percent) column,

'-'Su" should be S Col. 9, Table VI. Test 2, under E. percent solubilized,

Cu Column, "95.1" should be 97.5 A

. Col. 9, Table VII., under the column heading Wt. percent solubilized` across one stage, above the third column of numerals (after "Fe") add S as a column heading.

Col. 9, Table VII., Test 2, "state" should be stage Col. 9, Table VII., Test 5, under Size of material column,

"190" should be -100 Col. 9, line 63, "vapor-phase reaction" should be Vaporphase sulfidizing reaction Col. 13, line l2, "sulfrate" should be sulfate FORM P04050 (1o-69) uscoMM-Dc 60s76i=-e9 ILS. GOVERNMENT PRINTING OFFICE: 1959 0*-366-33! o* j .UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated June 18, 1974 Patent No. 3 r 817)'743 Ihvent-or') John B. Sardisco It is eerifed that error appears in the above-identified patent and that said Letters Patent are 'hereby corrected as shown below:

Col. l5, lines `2 -3, the phrase "with at least about 70% of the copper-Containing material in the reaction product" is repeated.

Col. 16, Aline. 5, f'prsssure" should be pressure Signed and sealed this 14th day of January 1975.

(SEAL) Atteetz v l McoY M. GIBSON JR. c. MARSHALL DANN n Atte'stng Cffoer Commissioner of Patents USCOMM-DC 60376-P69 U.S. GOVERNMENT PRINTING OFFICE |969 035633l 

